The crank arms are attached to the bottom bracket axle and have a pedal at the other end. Removing a left crank arm can be a tricky task because there are many different pedal arm fittings. But don’t worry, with our help and guidance you will be able to easily remove pedal arm on a 3 piece and 2 piece cranks including square taper, Hollowtech II and self extracting arms using the correct tools.
– Damaged pedal threads. If the pedal has been crossed threaded or insufficiently tightened then it may come off during a ride, most likely stripping the thread.
– Damaged crank/axle interface. If the crank arm wasn’t fitted correctly, it may come loose and eventually come off. Tightening it will not solve the problem as the damage has been done.
– Servicing/ replacing bottom bracket. To access the bottom bracket, the crank arms need to be removed first.
Tapered crank arm
The axle is conical, tapering at the crank end.
The crank hole is also conical and matches the axle.
As the bolt is tightened the crankset and axle are forced together, making it impossible to remove it by hand and a special tool is needed.
Tools required for a tapered crank arm removal
Crank extractor.
Adjustable spanner/allen key,
14mm socket/8mm allen key.
Small flat bladed screwdriver.
Removing left crank arm on a three piece crank
If you’re planning to replace the crank with a different one, first remove the pedal.
- If you have a dust cap, use the screwdriver to remove it
- Position the crank at 5 o’clock.
- Fit the 14mm socket or 8mm allen key as close to 7 o’clock as possible.
- Now holding the tool and crank with open hands, push them together until you feel the bolt release. This bolt will probably be really tight so expect to use a lot of force.
- If you grip the tools then when the bolt suddenly releases you may hurt your knuckles.
- Look at the threaded part of the crank bolt. If it’s a slim, solid piece then use the smaller end of the extractor. If it’s wide and hollow then use the larger end of the extractor.
- Unscrew the tool so that the extracting end is retracted.
- Now put a small amount of grease onto the threads of the extractor.
- Screw the extractor by hand clockwise into the crank arm. If, after repeated attempts it doesn’t go in, don’t force it as you can damage the thread. At this point seek further help.
- Once the tool is in, using the adjustable spanner, tighten the outer part.
- Now, by hand tighten the inner part of the tool clockwise until it stops.
- Put the crank arm at 9 o’clock and the allen key/ spanner at 2 o’clock. While holding the crank in place, screw the extractor clockwise until the crank comes off.
- Now while holding the crank unscrew the outer part of the extractor and remove the tool.
Hollowtech II™ system
The Hollowtech 11™ crank arm consists of the main body, two crank screws with washers that hold the crank arm in place, crank arm fixing bolt that compresses the chainset so that it doesn’t wobble but it spins smoothly, stopper plate with a locator that, when the crank is in position correctly, drops into the hole in the axle and stops the crank “walking” off it, and a crank o ring that applies pressure to the bottom bracket bearing .
The axle and the crank have interlocking splines. There are 2 thicker splines helping to locate the crank into the correct position.
Tools required for a Hollowtech II™ crank arm removal
5mm allen key.
Hollowtech 11™ crank arm tool.
Large flat bladed screwdriver.
Removing left crank arm on a Hollowtech II™ crank
- Loosen the crank arm bolts anti clockwise
- Remove the crank arm fixing screw by turning the tool anticlockwise.
- Lift the plate on the crank arm bolts.
- Release the crank arm by gently prising it away with the screwdriver and then pull it off.
Self extracting system
A Self extracting crank arm consists of the main body,
a crank retaining ring that is threaded and fitted in the arm and works as an extractor tool
and a crank bolt that pushes against the retaining ring until the arm comes away from the axle.
Tools required
Pin spanner/16mm allen key.
8mm/10mm allen key.
Removing self extracting left crank arm
- First make sure the retaining ring is tight. follow the arrows to tighten.
- Position the crank at 5 o’clock, fit the 8mm/10mm allen key as close to 7 o’clock as possible.
- Now holding the tool and crank with open hands, push them together until you feel the bolt release. This bolt will probably be really tight so expect to use a lot of force.
- Undo a little bit more until the bolt feels tight again. This is because it is butting up against the retaining ring.
- Now repeat the process of undoing the bolt until it feels loose. Once loose, keep unscrewing until the crank comes off. Make a note of any spacers or washers on the axle.
You can also watch our video tutorial here:
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A year ago, my left crank arm came loose and just keeps coming loose constantly now, no matter how much I tighten it. Do you have any suggestions?